14: The Autonomic Nervous System
Define autonomic nervous system and explain its relationship to the peripheral nervous system.
Compare the somatic and autonomic nervous systems relative to effectors, efferent pathways, and neurotransmitters released.
Compare and contrast the functions of the parasympathetic and sympathetic divisions. ANS Anatomy
For the parasympathetic and sympathetic divisions, describe the site of CNS origin, locations of ganglia, and general fiber pathways. ANS Physiology
Define cholinergic and adrenergic fibers, and list the different types of their receptors.
Describe the clinical importance of drugs that mimic or inhibit adrenergic or cholinergic effects.
State the effects of the parasympathetic and sympathetic divisions on the following organs: heart, blood vessels, gastrointestinal tract, lungs, adrenal medulla, and external genitalia.
Describe autonomic nervous system controls.
Homeostatic Imbalances of the ANS
Explain the relationship of some types of hypertension, Raynaud’s disease, and autonomic dysreflexia to disorders of autonomic functioning. Developmental Aspects of the ANS
Describe some effects of aging on the autonomic nervous system.
Suggested Lecture Outline
Introduction (pp. 526–528, Figs. 14.1–14.2)
Comparison of the Somatic and Autonomic Nervous Systems (pp. 526–527; Fig. 14.2) 1.
The somatic nervous system stimulates skeletal muscles, while the ANS innervates cardiac and smooth muscle and glands. 2.
In the somatic nervous system, the cell bodies of the neurons are in the spinal cord and their axons extend to the skeletal muscles they innervate. The ANS consists of a two-neuron chain. 3.
The neurotransmitter released by the somatic motor neurons is acetylcholine, which always has an excitatory effect; the neurotransmitters released by the ANS are epinephrine and acetylcholine, and both may have either an excitatory or an inhibitory effect. 4.
There is overlap between the somatic and autonomic nervous systems, and most body responses to changing internal and external stimuli involve both skeletal muscle activity and visceral organ responses. B.
Divisions of the Autonomic Nervous System (pp. 527–528; Fig. 14.1) 1.
The parasympathetic division keeps body energy use as low as possible while directing digestion and elimination activities. 2.
The sympathetic division prepares the body to respond to an emergency or threatening situation (or vigorous exercise).
ANS Anatomy (pp. 528–535; Figs. 14.3–14.8; Table 14.1) A.
Parasympathetic (Craniosacral) Division (pp. 529–530; Figs. 14.3–14.4; Table 14.1) 1.
The preganglionic axons extend from the CNS nearly all the way to the structures to be innervated, where they synapse with ganglionic neurons in the terminal ganglia. 2.
The cranial outflow consists of preganglionic fibers that run in the oculomotor, facial, glossopharyngeal, and vagus cranial nerves. 3.
The rest of the large intestine and the pelvic organs are served by the sacral outflow, which arises from neurons located in the lateral gray matter of spinal cord segments S2–S4. B.
Sympathetic (Thoracolumbar) Division (pp. 530–534; Figs. 14.3, 14.5–14.6; Table 14.1) 1.
The sympathetic division supplies the visceral organs in the internal body cavities but also all visceral structures in the somatic part of the body. 2.
When synapses are made in chain ganglia, the postganglionic axons enter the ventral (or dorsal) ramus of the adjoining spinal nerves by way of communicating branches called gray rami communicantes. 3.
The preganglionic fibers from T5 down synapse in collateral ganglia; thus these fibers enter and leave the sympathetic chains without synapsing. 4.
Some fibers of the thoracic splanchnic nerves terminate by synapsing with the hormone-producing medullary cells of the adrenal cortex. C.
The visceral sensory neurons are the first link in autonomic reflexes, sending information...
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